PAIN MECHANISMS - A REVIEW: I. Characteristics of the peripheral receptors

This paper is the first in a series summarizing recent developments in our understanding of pain mechanisms. While neural mechanisms must exist for the two components (perception and aversion) of pain experience, the prime role of pain systems is still unclear. The major difficulties encountered in experimentally evaluating pain are considered briefly, as it is essential that these be appreciated by workers in this field. General sensory mechanisms are briefly summarized, including factors determining whether conscious awareness of a stimulus occurs and the acuity of stimulus site localization. Nociceptors ("pain" receptors) are considered in terms of their structural characteristics and fibre groups. Although it is still unclear precisely how nociceptors are activated, their known functional characteristics probably provide the basis for distinguishing stabbing from burning pain, and for the sensations associated with primary hyperalgesia.